1. Field of the Invention
In a ground-based flight simulator it is desirable to produce the principal visual, audible, kinaesthetic and proprioceptive sensations of flight, and to model the behaviour of the vehicle so that these sensations can be changed dynamically.
2. Discussion of Prior Art
Motion contributes, greatly to the sensation of flight, but it is not possible to move the simulator cockpit with exact aircraft accelerations. Instead it may be mounted on a limited displacement motion platform with wash-out of enduring accelerations, or placed within the gondola of a centrifuge. The choice of platform, and its degrees of freedom, depends mainly upon the required severity and duration of the accelerations in relation to the precise objective of the simulation. However, the ill effects of inappropriate accelerations and overall system costs are also very important.
In high performance aircraft the strongest movement cues come from the centripetal accelerations induced by combat manoeuvres. Here the instantaneous load factor "gz", the ratio of the aircraft lift force to weight, can exceed a value of 8 for several tens of seconds. Since such effects can only be reproduced on the ground using extensive centrifuge facilities, designers of most training and research simulators abandon the attempt, and a fixed or limited displacement mounting is used. Comparatively enduring high g-cues may be supplied instead by secondary proprioceptive sensations, such as stick shake and seat hardening, or visually by darkening the external scene.
However, a far stronger mixture of proprioceptive cues and disturbances arises from the apparent weight change of the pilot's headgear under marioeuvring loads. Although in a real aircraft the g-forces would act on the pilot in a complex manner the major effect would be felt in what to him appears to be a vertical line, the forces acting upwards or downwards depending on the motion of the aircraft. This invention seeks to generate such an apparent weight change in a ground-based simulator by applying to the helmet a controlled vertical force, proportional to the instantaneous incremental load factor of the modelled aircraft.